Many electronic devices tend to require a highly responsive, low noise, high efficiency switching regulator.
Switching regulators emit output current ripple at their switching frequency. That current is converted to switching voltage noise when driving a resistive load. This type of noise can be disruptive to systems that amplify low level signals, for example, where the switching noise can couple into the circuitry and become amplified along with the desired signal. Harmonics of the switching frequency, in particular can generate noise into radio bands and produce spurious transmissions or desensitize receivers.
One option is to add filtering at the output of the switching regulator. Common L-C low-pass filters can be used. Unfortunately, filtering also limits the responsiveness of the switching regulator to abrupt changes in load, line, or voltage setting. Since the filters exhibit delay, it is generally not possible to include these filters inside the switching regulator's control loop for stability reasons. Thus, low noise and responsiveness are frequently tradeoffs against one another.
The switching frequency of the switching regulator could be increased, allowing a higher cutoff frequency filter. However, higher switching frequencies result in higher magnetics losses and higher switching losses, decreasing power conversion efficiency.
Therefore, there remains a need for a power supply that remains responsive, low noise, and maintains high efficiency.